ESA’s Planck satellite has revealed that the first stars in the Universe started forming later than previous observations of the Cosmic Microwave Background indicated. This new analysis also shows that these stars were the only sources needed to account for reionising atoms in the cosmos, having completed half of this process when the Universe had reached an age of 700 million years.
With the multitude of stars and galaxies that populate the present Universe, it’s hard to imagine how different our 13.8 billion year cosmos was when it was only a few seconds old. At that early phase, it was a hot, dense primordial soup of particles, mostly electrons, protons, neutrinos, and photons – the particles of light.
In such a dense environment the Universe appeared like an ‘opaque’ fog, as light particles could not travel any significant distance before colliding with electrons. … (ESA)